Process for producing pickles, and antimicrobial composition

ABSTRACT

The process for producing pickles of the invention comprises using an oil-in-water antimicrobial composition that contains allyisothiocyanate as the active ingredient and further contains surfactant and water added thereto, in any stage of producing pickles. The invention provides a process for stably producing pickles of good quality while taking suitable measures for surely suppressing the growth of microbes in producing pickles in a simplified manner. The antimicrobial composition of the invention comprises allyl isothiocyanate and a beta acids-containing hop extract as the active ingredients. This is useful as a food freshness-keeping agent free from all the problems with conventional AIT and hop extract each other.

TECHNICAL FIELD

The present invention relates to a process for producing pickles, and toan antimicrobial composition useful as a freshness-keeping agent forpickles and other various foods.

BACKGROUND ART

With the recent development of the technology of producing them, picklesare much produced by manufacturers that specialize in picklesproduction, and the consumption of vegetables to be pickled is nowincreasing. The yield of vegetables varies depending on the weather andother conditions, and the supply thereof is not all the time stable.Accordingly, for pickles of summer-season vegetables such as cucumbers,etc., Japanese pickles manufacturers import salted vegetables fromSoutheast Asian countries such as Taiwan and Thailand in whichsummer-season vegetables can be cropped any time throughout the year,and they produce pickles from the thus-imported salted vegetables. Theamount of salt added for salting vegetables varies depending on the typeof the vegetables and on the period of time for which the saltedvegetables shall be stored, but generally from a viewpoint of preventingthe decomposition of vegetables by propagation of microbes and securingpreservation stability, the amount of salt is extensive, because a highdegree of salinity is needed. Therefore, in the process of producingpickles from such salted vegetables, the salted vegetables must bedesalted and desalting them requires a large-scale apparatus and muchwater.

With the recent increase in health-oriented consumers, the consumptionof lightly-salted pickles such as those lightly preserved in salt, forexample, those lightly salted overnight rises. Concretely, the output ofvegetables lightly preserved in salt now amounts to ⅓ of the overalloutput of pickles in Japan, but in the production of such lightly-saltedpickles, the quality maintenance against microbial degradation is themost serious problem. Microbial degradation of lightly-salted picklesincludes rancidity, cloudiness and bag expansion, and these are causedby the propagation of microbes such as lactic acid bacteria and yeast.Accordingly, in production of lightly-salted pickles, it is a matter ofimportance how to prevent the propagation of such microbes.

On the other hand, in production of lightly-salted pickles, thetroublesome lactic acid bacteria and yeast are bearing the importantrole for brewing peculiar fermentation taste in manufacture of thepickles of others including fermentation pickles. However, if thepickles are too much fermented, their sour taste will be too strong andtheir smell will change and, as a result, their quality will lower.

As so mentioned hereinabove, microbes must be most optimally controlledin producing pickles, or that is, it is a matter of great importance howto control the activity of microbes in accordance with the type ofpickles to be produced. Given that situation, it is desired to provide amethod of surely controlling microbes in producing pickles in asimplified manner.

In this connection, it has heretofore been known that allylisothiocyanate (hereinafter referred to as AIT), one component of wasabi(Japanese horseradish) is highly antimicrobial against colibacillus andyeast, and is therefore useful for a food freshness-keeping agent.However, AIT is an oily liquid that has a peculiar pungent smell and ishighly volatile, and is therefore difficult to handle. Accordingly, ifAIT is used for antimicrobial purpose in producing pickles, thecomposition that contains AIT must be highly soluble in water and itsuse must be simple. JP-A No. 6-192018 discloses an antimicrobialcomposition that comprises AIT, a polyhydric alcohol and a surfactant,and it says that the composition is used for processing pickles.However, the composition is powdery and is not always satisfactory inpoint of its solubility in water. In addition, the composition must bemetered every time when a desired amount of AIT is dissolved inseasoning for pickles, and therefore, there is still room for improvingthe handlability of the AIT-containing composition.

For keeping the freshness of pickles and other various foods, AIT alonemay have a satisfactory antimicrobial spectrum in some cases and istherefore effective by itself for microbiostatic action in pickles andothers, but in some other cases, AIT alone is not satisfactory. Takingthe cases into consideration, it is desirable to combine AIT with anyother different type of antimicrobial component for enlarging theantimicrobial spectrum.

It is well known from the past that a hop extract has an antimicrobialactivity, and it is said that a hop extract gives a peculiar bittertaste to beer and retards the growth of microbes in beer. Theantimicrobial activity of the hop extract generally results from thebitter component of hops, alpha acids (humulones) and beta acids(lupulones); and the antimicrobial activity of the beta acids againstlactic acid bacteria is higher than that of alpha acids against them.However, the antimicrobial spectrum of the hop extract alone is notalways satisfactory.

In consideration of the above-mentioned matters, the present inventionis to provide a process for stably producing pickles of good qualitywhile taking suitable measures for surely suppressing the growth ofmicrobes in producing pickles in a simplified manner, and to provide anantimicrobial composition that is useful as a food freshness-keepingagent free from all the problems with conventional AIT and hop extracteach other.

DISCLOSURE OF THE INVENTION

The process for producing pickles of the invention that has beenattained in consideration of the above-mentioned matters is,characterized in that an oil-in-water antimicrobial composition whichcontains AIT as the active ingredient and further contains surfactantand water added thereto is used in any stage of producing pickles.

In the aforementioned production process the antimicrobial carpositioncan further contain a beta acids-containing hop extract as theadditional active ingredient.

In a further the production process the hop extract above is obtainedthrough extraction with liquid or critical-state carbon dioxide.

In a further production process the antimicrobial composition above isadded to saline water in which vegetables to be salted are dipped.

In a further production process the antimicrobial carposition above isadded to seasoning with which vegetables to be pickled are seasoned.

In the production process above, the pickles are lightly-salted pickles.

In the production process the pickles are additionally subdivided intosmall containers and the antimicrobial composition is added to thepickles before and/or after they are subdivided into small containers.

One antimicrobial composition of the invention contains AIT and a betaacids-containing hop extract as the active ingredients.

In the antimicrobial composition the hop extract is obtained throughextraction with liquid or critical-state carbon dioxide.

The antimicrobial composition can further contain surfactant and water,and is in the form of an oil-in-water preparation or a water-in-oilpreparation.

The food freshness-keeping agent of the invention comprises theantimicrobial composition.

The method of keeping the freshness of food comprises adding theantimicrobial composition to food.

JP-A No. 6-153882 discloses a combination of an antimicrobial substanceextracted and purified from horseradish (this may also be referred to aswasabi radish or Western wasabi), and a hop extract for use as a foodpreservative. However, the antimicrobial substance described in thispatent publication is a crystalline substance that is extracted andpurified from horseradish in a state of which a horseradish enzyme isinactivated or its enzymatic activity is blocked, and this substantiallydiffers from AIT that is an oily liquid as in the antimicrobialcomposition of the present invention. Prior to the present invention, noone knows an antimicrobial composition that comprises a combination ofAIT and a hop extract and its use.

BEST MODE OF CARRYING OUT THE INVENTION

The process for producing pickles of the invention is characterized inthat an oil-in-water antimicrobial composition which contains AIT as theactive ingredient and further contains surfactant and water addedthereto is used in any stage of producing pickles. The antimicrobialcomposition is a liquid preparation that contains a predetermined amountof AIT by itself, and its solubility in water is therefore high. Inaddition, a predetermined amount of AIT may be readily dissolved inseasonings and others in producing pickles, and therefore it excels inworkability.

AIT, the active ingredient of the antimicrobial composition may be anyand every one from natural substances and synthetic substances. As thecase may be, for example, it may be an AIT-containing essential oil, oran extract or a crude essential oil from wasabi or mustard. However,since it is added to pickles, a type of food, AIT is preferably anatural substance-derived one. In case where AIT is synthesized, theprocess for synthesizing it is not specifically defined. In general, forexample, allyl iodide or bromide is reacted with sodium thiocyanate inethanol under heat.

The surfactant usable in the invention may be any and every one selectedfrom those having an HLB value of from 1 to 20 in accordance with itsuse. Typical examples of the surfactant are glycerin fatty acid esters,sucrose fatty acid esters, sorbitan fatty acid esters, propylene glycolfatty acid esters, etc. Fatty acids referred to herein are meant togenerically include all fatty acids (straight chain fatty acids,branched chain fatty acids, saturated fatty acids, unsaturated fattyacids), and their examples are palmitic acid, stearic acid, myristicacid, oleic acid and lauric acid. As the case may be, phospholipids suchas various lecithins of, for example, soybean lecithin and egg yolklecithin, as well as hydrogenated phospholipids and sorbitan monooleatepolyoxyethylene (e.g., Tween 80-trade name) are also usable as thesurfactant herein.

The antimicrobial composition in the form of an oil-in-water preparationthat contains AIT as the active ingredient and further containssurfactant and water added thereto is a per-se known preparation and isdescribed, for example, in JP-A Nos. 6-47272 and 6-303952.

The matters to be pickled according to the process of the invention areto be side dishes that are directly eaten as they are, including, forexample, cabbage, Chinese cabbage, Nozawa rape, spinach, onion, beansprouts, butterbur, scallion, garlic, lotus root, Chinese (Japanese)white radish, turnip, carrot, burdock, potato, sweet potato, pumpkin,cucumber, eggplant, gourd, green ume (Japanese apricot), as well asother various fruits, mushrooms, seaweed (hereinafter these aregenerically referred to as vegetables) as main materials; and these arepickled in various seasonings of, for example, salt, soy sauce, miso(soybean paste), kasu (sake lees), koji (malted rice), vinegar, bran(e.g., rice bran, wheat bran), mustard, moromi (unrefined soy sauce,unrefined miso) and others. The resulting pickles may be ripened andtherefore fermented to thereby further enhance their preservation insalt, alcohol or acid; or different from these, some vegetables may belightly salted and seasoned only overnight, and the preservability ofthe thus lightly-salted pickles is not so good.

Depending on the seasonings used, pickles are grouped into saltedpickles for which the seasoning used consists essentially of salt (e.g.,salted scallion, yellow pickled radish, salted ume, salted Nozawa rape);soy sauce pickles for which the seasoning used consists essentially ofsoy sauce (e.g., sliced vegetables pickled in soy sauce, leaf mustardpickled in soy sauce, Korean pickles); miso pickles for which theseasoning used consists essentially of miso (e.g., edible wild plantspickled in miso, Japanese white radish pickled in miso); kasu picklesfor which the seasoning used consists essentially of kasu (e.g., gourdpickles, wasabi preserved in kasu); koji pickles for which the seasoningused consists essentially of koji (e.g., Japanese white radish pickledin sweetened koji, Sagohachi pickles); vinegar pickles having a pH of atmost 4.0, for which the seasoning used consists essentially of ediblevinegar, ume vinegar or organic acid (e.g., sliced Japanese white radishpickled in vinegar, scallion pickled in vinegar, Japanese white radishpickled in sweetened vinegar); bran pickles for which the seasoning usedconsists essentially of bran (e.g., Japanese white radish pickled inbran); mustard pickles for which the seasoning used consists essentiallyof mustard powder (e.g., eggplant pickles in mustard, butterbur pickledin mustard); moromi pickles for which the seasoning used consistsessentially of moromi of unrefined soy sauce or unrefined miso (e.g.,small eggplant pickled in moromi, cucumber pickled in moromi); and otherpickles than the above (including fermented pickles) such as turnippickles and sauerkrauts.

The antimicrobial composition in the form of an oil-in-water preparationthat contains AIT as the active ingredient and further containssurfactant and water added thereto may be used in any stage of producingthe pickles in which the pickles being produced must be protected frommicrobes. For example, the antimicrobial composition preparation may beused in the process as follows: The preparation is dispersed in salinewater for salting vegetables or in various seasonings for seasoningthem; or the preparation is dispersed in water and the resultingdispersion is sprayed on vegetables to be into pickles; or vegetables tobe into pickles are washed with the dispersion. In any of these methods,it is desirable that the AIT concentration in the AIT-containingsolution is specifically so controlled as to fall between 1 ppm and 500ppm in order that AIT is well effective for suppressing the growth ofmicrobes such as colibacillus in the pickles produced and that AIT doesnot give too much pungent smell and bitter taste peculiar to AIT to thepickles. In case where the antimicrobial composition is added toseasoning for pickles, consumers that take the pickles will also takethe seasoning along with the pickles. In that case, therefore, it isdesirable that the uppermost limit of the AIT concentration that may bein the seasoning is as low as possible, concretely at most 150 ppm.

For example, in the embodiment of adding the antimicrobial compositionto saline water in the process of preserving vegetables in salt, evenwhen the amount of salt added to vegetables is reduced, the propagationof microbes in the salted vegetables is effectively prevented owing tothe action of the antimicrobial composition added to the saline water,and, as a result, the salted vegetables enjoy satisfactory preservationstability. Accordingly, the salted vegetables can be readily desalted,not requiring any large-scal apparatus and much water.

In another embodiment of adding the antimicrobial composition toseasoning in which vegetables are lightly pickled, the antimicrobialcomposition having been previously added to the seasoning surelyprevents the degradation of lightly-salted pickles such as rancidity,cloudiness and bag expansion thereof, which are caused by thepropagation of microbes such as lactic acid bacteria. In otherembodiments of producing pickles, the antimicrobial composition may beadded to seasoning in the stage in which the seasoned pickles arefermented moderately, whereby the pickles are prevented from being toomuch fermented and the fermented pickles are therefore prevented frombeing degraded. Concretely, for example, the pickles are prevented fromturning too sour or from having any offensive smell.

In case where the pickles produced are subdivided into small containers,the antimicrobial composition may be added to them before and/or afterthey are subdivided into small containers. In this embodiment, thepickles having been subdivided into small containers are prevented frombeing fermented, or that is, they are prevented from being degraded toturn too sour or to have any offensive smell.

The antimicrobial composition that contains AIT and a betaacids-containing hop extract as the active ingredients is also usefulfor microbiostatic action in producing pickles. As so mentionedhereinabove, the antimicrobial composition that comprises a combinationof AIT and a hop extract and its use are unknown, and the antimicrobialcomposition of the type is per se novel and constitutes a part of theinvention.

In this embodiment, AIT that serves as the active ingredient of theantimicrobial composition may be the same as that mentioned hereinabove.

For obtaining the beta acids-containing hop extract that is anotheractive ingredient of the antimicrobial composition of this embodiment,preferably employed is a method of extraction of hops with liquid orcritical-state carbon dioxide. (This method is per se known. If desired,referred to are JP-A Nos. 61-1374 and 6-240288.) According to thismethod, a hop extract generally containing at least 50% by weight ofbeta acids (the residue is hop resin or hop essential oil) isefficiently obtained. The extract obtained according to the method isavailable on the market. For example, one commercially-available productis EHP BASE EXTRACT (trade name) produced by ENGLISH HOP PRODUCTSLIMITED. The method of preparing the beta acids-containing hop extractis not limited to the above-mentioned one. Apart from it, for example,hops may be extracted with cold water or hot water; or they may beextracted with an organic solvent such as ether, ethanol, acetone,chloroform or ethyl acetate; or they may be extracted with an aqueoussolution of alkali such as sodium hydroxide, sodium carbonate, ammoniumcarbonate or sodium phosphate.

The blend ratio of AIT to the beta acids-containing hop extract in thecomposition preferably falls between 5:1 and 1:1 by weight. Combined inthe ratio falling within the range, both AIT and the betaacids-containing hop extract in the composition well exhibit their bestability to suppress the growth of microbes. Another advantage of thecomposition is that the beta acids-containing hop extract can bedissolved in AIT even in the absence of an organic solvent to therebygive a uniform solution of the antimicrobial composition comprising thetwo. Since AIT is reactive with ethanol, the use of too much ethanol forthe solvent in the antimicrobial composition of the invention isundesirable. The blend ratio of the two active ingredients fallingwithin the range defined as above is enough for the individualingredients, AIT and beta acids-containing hop extract to well exhibittheir best ability to suppress the growth of microbes and is enough forthe constitutive ingredients to be formulated into good preparations.

The antimicrobial composition that contains AIT and a betaacids-containing hop extract as the active ingredients may form auniform solution when the two ingredients therein are in the ratiodefined as above, and therefore can be used as a food freshness-keepingagent in any desired preparation form. For better handlability andpopularity thereof, it is desirable that the antimicrobial compositionfurther contains surfactant and water to be an oil-in-water preparationor a water-in-oil preparation for practical use.

For the surfactant that may be in the composition, referred to are thosementioned hereinabove.

A method of formulating the antimicrobial composition that contains AITand a beta acids-containing hop extract as the active ingredients in toan oil-in-water preparation is described below.

For formulating the antimicrobial composition into the intendedoil-in-water preparation, from 1 to 100 parts by weight, preferably from4 to 20 parts by weight of water is added to one part by weight of thecomposition. The surfactant that may be added to the antimicrobialcomposition is preferably one having an HLB value of from 8 to 16, andits amount is from 0.01 to 1 parts by weight, preferably from 0.02 to0.5 parts by weight relative to one part by weight of the composition.

The constitutive components may be mixed and emulsified in any per seknown method, for example, in a homogenizer or homomixer.

A method of formulating the antimicrobial composition that contains AITand a beta acids-containing hop extract as the active ingredients into awater-in-oil preparation is described below.

For formulating the antimicrobial composition into the intendedwater-in-oil preparation, from 1 to 100 parts by weight, preferably from4 to 40 parts by weight of water is added to 100 parts by weight of thecomposition. The surfactant that may be added to the antimicrobialcomposition is preferably one having an HLB value of from 1 to 4, andits amount is from 1 to 100 parts by weight, preferably from 4 to 40parts by weight relative to 100 parts by weight of the composition. Incase where the antimicrobial composition is formulated into such awater-in-oil preparation, it is desirable that an emulsion stabilizerof, for example, saccharides such as maltose or sorbitol and athickening agent such as gum arabic or carboxymethyl cellulose are addedto the composition. The amount of the saccharide that may be added tothe antimicrobial composition may fall between 1 and 100 parts byweight, but preferably between 10 and 50 parts by, weight relative to100 parts by weight of the composition; and the amount of the thickeningagent that may also be added thereto may fall between 0.01 and 10 partsby weight, but preferably between 0.1 and 5 parts by weight relative to100 parts by weight of the composition.

The constitutive components may be mixed and emulsified in any per seknown method, for example, in a homogenizer or homomixer.

The antimicrobial composition that contains AIT and a betaacids-containing hop extract as the active ingredients serves as a foodfreshness-keeping agent that effectively suppresses the growth ofmicrobes such as lactic acid bacteria and colibacillus in foods, and isused, for example, for pickles such as those mentioned hereinabove, andalso for other foods such as everyday dishes essentially made fromcereals and vegetables (e.g., foods boiled down in soy sauce); kneadedmarine products such as boiled fish pastes, tube-shaped fish pastecakes; delicacies of marine products; processed meat products such assausages, bacons, hamburgers and meat balls; noodles and various saucesand seasonings.

In particular, in case where the antimicrobial composition of theinvention is used in the form of an oil-in-water preparation or awater-in-oil preparation, it maybe used in various methods, for example,by dispersing the preparation in water to form a dispersion, and thenthe dispersion is added to food materials at a mixing step, sprayed onthe foods after heating and shaping, or added to seasonings, or thefoods are dipped in the dispersion, or the foods are washed with thedispersion. In those cases, the dispersion is preferably so designedthat the AIT concentration and the beta acids-containing hop extractconcentration therein each fall between 0.1 and 1000 ppm. If the AITconcentration in the dispersion is lower than the defined range, thedispersion may be ineffective for suppressing the growth of microbessuch as colibacillus; but if higher than it, the pungent smell and thebitter taste peculiar to AIT may remain in the foods treated with thedispersion. On the other hand, if the beta acids-containing hop extractconcentration is lower than the defined range, the dispersion may beineffective for suppressing the growth of microbes such as lactic acidbacteria; but if higher than it, the bitter taste peculiar to hops mayremain in the foods treated with the dispersion.

For the pickles to which the antimicrobial composition that contains AITand a beta acids-containing hop extract as the active ingredients isapplied while they are produced, referred to are those mentionedhereinabove.

The antimicrobial composition that contains AIT and a betaacids-containing hop extract as the active ingredients may be used inany stage of producing the pickles in which the pickles being producedmust be protected from microbes. For example, when the antimicrobialcomposition is used in the form of an oil-in-water preparation or awater-in-oil preparation thereof, it may be applied to pickles invarious methods. Concretely, the preparation is dispersed in salinewater for salting vegetables or in various seasonings for seasoningthem; or the preparation is dispersed in water and the resultingdispersion is sprayed on vegetables to be into pickles; or vegetables tobe into pickles are washed with the dispersion. In any of these methods,the solution containing AIT and a beta acids-containing hop extract ispreferably so designed that the AIT concentration and the betaacids-containing hop extract concentration therein each fall between 1and 500 ppm, in order that AIT in the solution is well effective forsuppressing the growth of microbes such as colibacillus in the picklesproduced, not giving to the pickles too much pungent smell and bittertaste peculiar to AIT, and in order that the beta acids-containing hopextract is well effective for suppressing the growth of microbes such aslactic acid bacteria in the pickles produced, not giving to the picklestoo much bitter taste peculiar to hops. In case where the antimicrobialcomposition is added to seasoning for pickles, consumers that take thepickles will also take the seasoning along with the pickles.Accordingly, the AIT concentration and the beta acids-containing hopextract concentration in the seasoning are preferably as low aspossible. Concretely, it is desirable that the two are at most 150 ppmeach.

When the antimicrobial composition that contains AIT and a betaacids-containing hop extract as the active ingredients is used inproducing pickles, the beta acids-containing hop extract therein surelyacts to suppress the growth of microbes such as lactic acid bacteriawhile AIT therein also surely acts to suppress the growth of othermicrobes such as yeast, and therefore the pickles produced are surelyprevented from being degraded by microbes such as lactic acid bacteriaand yeast. Concretely, for example, the pickles are free from rancidity,cloudiness and bag expansion that may be caused by the propagation ofmicrobes therein. In addition, deterioration of the commercial value ofthe packaged pickles by the bag expansion based on the fermentationunder the anaerobiosis of lactic acid bacteria can be prevented.

EXAMPLE

The invention is described in more detail with reference to thefollowing Examples, which, however, are not intended to restrict thescope of the invention.

Example 1

A. Preparation of AIT-Containing, Oil-in-Water AntimicrobialComposition:

5 parts by weight of mustard oil having an AIT content of 94% by weight,1 part by weight of purified coconut oil (from Nisshin Oil Mills), 2parts by weight of commercial soybean lecithin (having a lecithincontent of 50% by weight), and 1 part by weight of a surfactant havingan HLB value of 15 (sucrose palmitate), Ryoto Sugar Ester P-1570 (tradename by Mitsubishi Kagaku Foods) were emulsified in 91 parts by weightof water with a homogenizer to prepare an oil-in-water emulsion. Theemulsion is milky. Even after stored at room temperature for 20 days, nophase separation was seen therein, and the emulsion is extremely stable.One part by weight of the emulsion was added to and suspended in 100parts by weight of water, and it gave a uniform dispersion.

B. Effect of the Antimicrobial Composition in Producing Pickles:

Scallions were pickled in sweetened vinegar in the following manner. Acontrol seasoning was prepared from 500 ml of edible vinegar having anacid content of 5% by weight, 1400 ml of water, 250 g of sugar, 15 g ofsalt and 3 g of sodium glutamate. To this added was 0.01% by weight,0.02% by weight or 0.04% by weight of the antimicrobial compositionprepared in the above step A. Salted scallions were desalted in water,and these were pickled in any of these seasonings, divided into smallportions, put into styrene containers, and stored at room temperature.These were visually observed with the naked eyes as to whether or notfilm forming yeast grow in the stored pickles. The results are shown inTable 1. As is obvious from Table 1, even the seasoning having such alow degree of acidity effectively suppressed the growth of film formingyeast in the pickled scallions when the antimicrobial composition wasadded to the seasoning, and the period for which the pickled scallionsare kept fresh is prolonged.

TABLE 1 Amount of Growth of film forming yeast Antimicrobial at theafter Composition start 7 after after after after Added (wt. %) of testdays 14 days 28 days 42 days 56 days 0 − − ± ++ +++ NOT TESTED 0.01¹⁾ −− − ± + +++ 0.02²⁾ − − − − − ± 0.04³⁾ − − − − − − −: no change; ±:slightly grown; +: grown; ++: grown in a wide range; +++: much growneverywhere. ¹⁾AIT concentration 5 ppm ²⁾AIT concentration 10 ppm ³⁾AITconcentration 20 ppm

Example 2 Antimicrobial Effect of AIT and Beta Acids-Containing HopExtract

The antimicrobial activity of AIT and beta acids-containing hop extractagainst Lactobacillus plantarum, Escherichia Coli, Staphylococcus aureusand Hansenula anomala was investigated in the manner mentioned below.The beta acids-containing hop extract used herein is EHP BASE EXTRACT(trade name) produced by ENGLISH HOP PRODUCTS LIMITED.

(Method)

10 ppm AIT solution (sample A2), 20 ppm AIT solution (sample A3), 40 ppmAIT solution (sample A4) and 80 ppm AIT solution (sample A5) wereprepared, each in 0.1% Tween 80 solution. Compared with these, 0 ppm AITsolution (sample Al) was also prepared, and this is 0.1% Tween 80solution. On the other hand, 5 ppm beta acids-containing hop extractsolution (sample H2), 10 ppm hop extract solution (sample H3), 20 ppmhop extract solution (sample H4) and 40 ppm hop extract solution (sampleH5) were prepared, each in 0.1% Tween 80 solution. Compared with these,0 ppm hop extract solution (sample Hl) was prepared, and this is 0.1%Tween 80 solution.

Test tubes each filled with 8 ml of a brain heart infusion broth medium(BHI medium) were sterilized, and a combination Qf any of samples A andany of samples H of 1 ml each was added to every test tube and mixedwith the medium therein. With that, 0.1 ml (10³ cfu) of any of differenttest microbe cell suspensions was inoculated into the medium andincubated therein at 30° C. The incubation time is the optimum growthtime for each test microbe, and is as in Table 2. After the cells werethus incubated therein, the turbidity of each medium at 660 nm wasmeasured to evaluate the antimicrobial activity (cell growth inhibitionpercentage) of AIT and the beta acids-containing hop extract against thetest microbes. (For Hansenula anomala cells, an YM liquid medium wasused in place of the BHI medium.)

TABLE 2 Microbes Incubation Time L. plantarum 24 hours E. coli 18 hoursS. aureus 18 hours H. anomala 7 days(Result)

Table 3 shows the antimicrobial activity of the antimicrobialcomposition samples against Lactobacillus plantarum. As is obvious fromTable 3, sample H4 and sample H5 almost completely suppressed the growthof the cells irrespective of the AIT content of samples A combined withthem. On the other hand, the antimicrobial activity of sample H2 andsample H3 increases with the increase in the AIT content of samples Acombined with them. This confirms the combined use effect of thecombination of samples A and samples H.

TABLE 3 Cell Growth Inhibition AIT Percentage (%) against Sample SampleSample Sample Sample L. plantarum A1 A2 A3 A4 A5 Beta Sample H1 0 23 4842 48 Acids- Sample H2 34 32 55 57 69 containing Sample H3 83 82 87 8996 Hop Sample H4 97 97 97 97 97 Extract Sample H5 99 100 99 99 100

Against Escherichia Coli, the antimicrobial composition samplescompletely suppressed the growth of the cells so far as the AIT contentthereof is not lower than the level of sample A3, irrespective of thebeta acids-containing hop extract content of samples H combined withsamples A in the composition samples. Against Staphylococcus aureus, theantimicrobial composition samples completely suppressed the growth ofthe cells so far as the AIT content thereof is not lower than the levelof sample A4, irrespective of the beta acids-containing hop extractcontent of samples H combined with samples A in the composition samples.Against Hansenula anomala, the antimicrobial composition samplescompletely suppressed the growth of the cells so far as the AIT contentthereof is not lower than the level of sample A2, irrespective of thebeta acids-containing hop extract content of samples H combined withsamples A in the composition samples.

Example 3 Preparation of Oil-in-Water Antimicrobial Composition thatContains AIT and Beta Acids-Containing Hop Extract

5 parts by weight of AIT, 2.5 parts by weight of beta acids-containinghop extract, and 1 part by weight of a surfactant having an HLB value of15 (sucrose stearate), Kyoto Sugar Ester 5-1570 (trade name byMitsubishi Kagaku Foods) were emulsified in 91.5 parts by weight ofwater with a homogenizer to prepare an oil-in-water emulsion. Theemulsion is flesh-colored milky. Even after stored at room temperaturefor 20 days, no phase separation was seen therein, and the emulsion isextremely stable. One part by weight of the emulsion was added to andsuspended in 100 parts by weight of water, and it gave a uniformdispersion.

Example 4 Preparation of Water-In-Oil Antimicrobial Composition thatContains MT and Beta Acids-Containing Hop Extract:

33.5 parts by weight of AIT, 16.5 parts by weight of betaacids-containing hop extract, 15 parts by weight of a surfactant havingan HLB value of 2 (sucrose palmitate), Ryoto Sugar Ester P-270 (tradename by Mitsubishi Kagaku Foods), 20 parts by weight of an emulsionstabilizer, maltose, and 15 parts by weight of water were mixed andstirred in a homomixer to prepare a water-in-oil emulsion. The emulsionis yellowish milky and creamy. Even after stored at room temperature for20 days, no phase separation was seen therein, and the emulsion isextremely stable. One part by weight of the emulsion was added to andsuspended in 100 parts by weight of water, and it gave a uniformdispersion.

Example 5 Freshness-Keeping Effect for Noodles of AntimicrobialComposition of Example 3

The antimicrobial composition (0.2 ml, 0.4 ml, 0.6 ml) and 10 g of saltwere suspended and dissolved in 370 ml of tap water, to which was added1000 g of wheat flour. This was stirred in a mixer for 20 minutes andthen rolled into a sheet of noodle-to-be. This was ripened at roomtemperature for 2 hours, then further rolled, and thereafter cut intonoodles having a width of 3 mm. Thus obtained, the noodles were put intoa polyethylene-aluminium laminate bag, then heat-sealed, and stored at30° C. Each bag with the noodles therein was checked for expansion. Theresults are shown in Table 4. As is obvious from Table 4, theantimicrobial composition added to the noodles effectively suppressedthe growth of microbes in the noodles and the bags with the noodlestherein were prevented from expanding.

TABLE 4 Period of Storage (day) 0 3 5 7 10 14 18 AntimicrobialComposition not added − ± + + ++ NOT NOT TESTED TESTED Amount ofAntimicrobial Composition Added A B C 0.2 ml 0.02 27 13.5 − − − + + ++NOT TESTED 0.4 ml 0.04 54 27   − − − − + ++ NOT TESTED 0.6 ml 0.06 8140.5 − − − − − ± + A: Ratio to wheat flour (%) B: AIT concentration intap water (ppm) C: Beta acids-containing hop extract concentration intap water (ppm) * −: not expanded, ±: expanded but a little, +:expanded, ++: much expanded like balloon.

Example 6 Effect of Antimicrobial Composition of Example 3 in PreservingVegetables in Salt (Preservation of Cucumbers in Salt)

Cucumbers were well washed with water. At room temperature, these werepreserved in saline water of different concentrations, of which theweight is the same as that of the cucumbers and which contains theantimicrobial composition of a different concentration. While thecucumbers were preserved therein, the saline water was analyzed for thestandard plate count therein by cultivating a sample of the saline waterin a standard agar medium (according to the Standard Methods of Analysisin Food Safety Regulation—the same shall apply hereinunder). The resultsare shown in Table 5. As is obvious from Table 5, even 5% by weight ofsaline water effectively suppressed the growth of microbes when theantimicrobial composition was added thereto. It is also understood fromit that the antimicrobial effect of 10% by weight of saline water thatcontains 0.2% by weight of the antimicrobial composition added theretois almost the same as that of 20% by weight of saline water that isgenerally used for salting preservation of vegetables therein, and thatthe antimicrobial effect of 10% by weight of saline water that contains0.4% by weight of the antimicrobial composition added thereto is higherthan that of 20% by weight of saline water. The result confirms thatadding the antimicrobial composition to saline water significantlyreduces the salt content of saline water necessary for saltingpreservation of vegetables therein.

TABLE 5 Amount of Concentration Antimicrobial Standard Plate Count(CFU/g) of Saline Composition at the start Water (wt. %) Added (wt. %)of test after 7 days after 21 days after 35 days after 56 days  5 0 4.8× 10⁵ 6.5 × 10⁸ NOT TESTED NOT TESTED NOT TESTED 0.2¹⁾ 4.8 × 10⁵ 7.0 ×10³ 3.5 × 10⁴ 8.6 × 10⁵ 1.6 × 10⁸ 0.4²⁾ 4.8 × 10⁵ 3.0 × 10² 9.8 × 10²3.3 × 10⁴ 4.3 × 10⁵ 10 0 4.8 × 10⁵ 1.1 × 10⁵ 1.5 × 10⁶ 2.4 × 10⁷ 3.2 ×10⁸ 0.2 4.8 × 10⁵ 7.0 × 10² 7.0 × 10² 5.6 × 10³ 8.6 × 10⁴ 0.4 4.8 × 10⁵1.4 × 10² 2.0 × 10² 5.6 × 10² 2.3 × 10³ 15 0 4.8 × 10⁵ 3.2 × 10⁴ 9.8 ×10⁴ 7.3 × 10⁴ 6.8 × 10⁴ 0.2 4.8 × 10⁵ 4.5 × 10² 5.0 × 10² 7.4 × 10² 3.2× 10³ 0.4 4.8 × 10⁵ 1.3 × 10² 1.7 × 10² 6.1 × 10² 2.2 × 10³ 20 0 4.8 ×10⁵ 1.4 × 10³ 8.0 × 10⁴ 1.6 × 10⁴ 2.3 × 10⁴ ¹⁾AIT concentration 100 ppm;beta acids-containing hop extract 50 ppm ²⁾AIT concentration 200 ppm;beta acids-containing hop extract 100 ppm

Example 7 Effect of Antimicrobial Composition of Example 3 in PicklingVegetables in Seasoning (Lightly-Salted Cucumbers)

Cucumbers were well washed with water. For 5 hours at room temperature,these were pickled in 5% by weight of saline water of which the weightis the same as that of the cucumbers. This is pre-pickling in salinewater. Thus pre-pickled, the cucumbers become flexible. Then, these werepickled in a seasoning liquid (containing 2% by weight of salt and 0.1%by weight of sodium glutamate), of which the weight is the same as thatof the cucumbers and which contains the antimicrobial composition of adifferent concentration. With that, these were put into polyethylenebags, and stored at 10° C. The turbidity, if any, of the seasoningliquid resulting from the growth of microbes in the bags was measuredwith a calorimeter (OD 660 nm). The results are shown in Table 6.Regarding the turbidity of the seasoning liquid in which the pickles arelightly pickled, it is generally said that the degree of lighttransmittance of the seasoning liquid must be at least 70% forsatisfying the commercial-level requirement of pickles. As is obviousfrom Table 6, the seasoning liquid could not have a degree of lighttransmittance of at least 70% on day 4 when no antimicrobial compositionis added thereto, but adding the antimicrobial composition to theseasoning liquid has prolonged the period for stable storage of thepickles in accordance with the amount of the composition added thereto.The antimicrobial composition added to the seasoning liquid had noinfluence on the taste of the pickles produced.

TABLE 6 Amount of Light Transmittance (%) Antimicrobial at theComposition start after after after after after Added (wt. %) of test 3days 4 days 5 days 6 days 7 days 0 99.9 93.4 52.4 24.7 9.5 5.6 0.05¹⁾98.7 98.5 84.1 37.7 14.0 7.5 0.1²⁾ 98.0 98.2 97.3 82.0 42.8 19.8 0.15³⁾98.0 96.7 97.8 97.5 91.4 44.2 ¹⁾AIT concentration 25 ppm, betaacids-containing hop extract 12.5 ppm ²⁾AIT concentration 50 ppm, betaacids-containing hop extract 25 ppm ³⁾AIT concentration 75 ppm, betaacids-containing hop extract 37.5 ppm

Example 8 Effect of Antimicrobial Composition of Example 3 in PicklingVegetables in Seasoning (Lightly-Salted Chinese Cabbages)

Outer leaves were removed from Chinese cabbages, and each cabbage wascut into four and then well washed with water. For 5 hours at roomtemperature, these were pickled in 5% by weight of saline water of whichthe weight is the same as that of the chinese cabbages. This ispre-pickling in saline water. Thus pre-pickled, the cabbages werelightly squeezed to remove water, and then pickled in a seasoning liquid(containing 2% by weight of salt and 0.1% by weight of sodiumglutamate), of which the weight is the same as that of the cabbages andwhich contains the antimicrobial composition of a differentconcentration. With that, these were put into polyethylene bags, andstored at 10° C. The turbidity, if any, of the seasoning liquidresulting from the growth of microbes in the bags was measured with acolorimeter (OD 660 nm). The results are shown in Table 7. In addition,the standard plate count in the seasoning liquid was counted byincubating the seasoning liquid in a standard agar medium. The resultsare shown in Table 8. Further, the number of lactic acid bacteria in theseasoning liquid was counted by incubating in an MRS agar medium, andthe results are shown in Table 9; the number of fungus in the seasoningliquid was counted by incubating in a PDA medium, and the results areshown in Table 10. As is obvious from Tables 7 to 10, adding theantimicrobial composition to the seasoning liquid effectively preventedthe turbidity increase of the seasoning liquid and suppressed the growthof microbes therein, and, as a result, the period for stable storage ofthe pickles in the seasoning liquid is thereby prolonged.

TABLE 7 Amount of Antimicrobial Light Transmittance (%) Composition atthe start of after after after after Added (wt. %) test 3 days 5 days 7days 10 days 0 99.5 94.5 43.2 NT NT 0.05¹⁾ 99.4 96.8 50.7 40.0 NT 0.1²⁾99.2 97.5 85.3 47.6 NT 0.15³⁾ 99.3 98.0 96.3 92.3 45.2 ¹⁾AITconcentration 25 ppm, beta acids-containing hop extract 12.5 ppm ²⁾AITconcentration 50 ppm, beta acids-containing hop extract 25 ppm ³⁾AITconcentration 75 ppm, beta acids-containing hop extract 37.5 ppm NT: nottested.

TABLE 8 Amount of Anti- microbial Composition Standard Plate Count(CFU/g) Added at the start after after after after (wt. %) of test 3days 5 days 7 days 10 days 0 1.4 × 10⁴ 6.4 × 10⁶ 5.2 × 10⁸ 7.3 × 10⁹ 6.7× 10⁹ 0.05 1.4 × 10⁴ 8.3 × 10⁵ 3.3 × 10⁷ 2.5 × 10⁸ 7.4 × 10⁹ 0.1 1.4 ×10⁴ 5.7 × 10⁴ 4.8 × 10⁵ 5.4 × 10⁶ 3.4 × 10⁸ 0.15 1.4 × 10⁴ 9.4 × 10³ 2.8× 10⁴ 3.7 × 10⁵ 7.6 × 10⁷

TABLE 9 Amount of Anti- microbial Composition Number of lactic acidbacteria (CFU/g) Added at the start after after after after (wt. %) oftest 3 days 5 days 7 days 10 days 0 3.4 × 10⁴ 9.8 × 10⁵ 7.2 × 10⁷ 2.3 ×10⁹ 5.3 × 10⁹ 0.05 3.4 × 10⁴ 2.3 × 10⁴ 4.5 × 10⁶ 7.0 × 10⁸ 5.5 × 10⁹ 0.13.4 × 10⁴ 8.9 × 10³ 9.7 × 10⁴ 7.9 × 10⁵ 6.1 × 10⁷ 0.15 3.4 × 10⁴ 5.6 ×10³ 1.6 × 10⁴ 9.9 × 10⁴ 3.8 × 10⁶

TABLE 10 Amount of Anti- microbial Composition Number of fungus (CFU/g)Added at the start after after after after (wt. %) of test 3 days 5 days7 days 10 days 0 5.3 × 10⁴ 2.2 × 10⁵ 6.8 × 10⁶ 5.6 × 10⁷ 6.6 × 10⁷ 0.055.3 × 10⁴ 3.8 × 10⁴ 2.9 × 10⁵ 8.9 × 10⁶ 5.3 × 10⁷ 0.1 5.3 × 10⁴ 9.9 ×10² 6.9 × 10³ 1.7 × 10⁵ 7.4 × 10⁶ 0.15 5.3 × 10⁴ 1.5 × 10² 3.6 × 10² 4.6× 10³ 4.8 × 10⁵

Example 9 Effect of Antimicrobial Composition of Example 3 inSubdividing Pickles into Small Containers (Storing Soy Sauce-SeasonedCucumbers in Small Cups)

Salted cucumbers were well washed with water and cut into pieces. Thesewere desalted by rinsing them in running water for 5 hours. Thusdesalted, the cucumbers were well dewatered by centrifuging them, andthereafter seasoned with a seasoning (containing 67% by weight of soysauce, 0.3% by weight of sodium glutamate, and 0.03% by weight of sodiumsuccinate). Thus seasoned, the cucumbers were divided into smallportions and put into commercially-available plastic cups (300 ml involume, with a lid), whereupon the antimicrobial composition of adifferent concentration was added to every cup. With the thus-seasonedcucumbers therein, the cups were stored at 15° C. While stored, the cupswere observed with the naked eyes as to how film forming yeast grow andhow the cups expand. The results are shown in Table 11 and Table 12. Asis obvious from Table 11 and Table 12, film forming yeast began to growon day 4 in the cups with no oil-in-water preparation therein, and onday 7, the cups began to expand. As opposed to these, the cups with theantimicrobial composition therein are free from these troubles, or thatis, the antimicrobial composition added to the cups effectivelysuppressed the growth of microbes in pickles, and the period for stablestorage of the pickles in the cups that contain the antimicrobialcomposition is prolonged.

TABLE 11 Amount of Growth of film forming yeast Antimicrobial at theComposition start after after after after after Added (ml) of test 2days 4 days 7 days 10 days 14 days 0 − − ± + ++ +++ 0.01 − − − + + ++0.02 − − − ± ± + 0.04 − − − − − − −: no grown; ±: slightly grown; +:grown; ++: grown in a wide range; +++: much grown everywhere.

TABLE 12 Amount of Cup Expansion Antimicrobial at the Composition startafter after after after after Added (ml) of test 2 days 4 days 7 days 10days 14 days 0 − − − + + + 0.01 − − − − + + 0.02 − − − − − + 0.04 − − −− − − − Not expanded. + Expanded.

INDUSTRIAL APPLICABILITY

According to the present invention, an oil-in-water antimicrobialcomposition that contains, as the active ingredient, AIT, highlyeffective for suppressing the growth of colibacillus and yeast, andfurther contains surfactant and water added thereto is used in any stageof producing pickles, and the invention provides a process for stablyproducing pickles of good quality while taking suitable measures forsurely suppressing the growth of microbes in producing pickles in asimplified manner,

The antimicrobial composition that the invention provides for pickles,contains, as the active ingredients, AIT which is effective forsuppressing the growth of colibacillus and yeast, and a betaacids-containing hop extract which is effective for suppressing thegrowth of lactic acid bacteria. In the antimicrobial composition of thetype, the ratio of AIT to the beta acids-containing hop extract may besuitably controlled, and the beta acids-containing hop extract can bewell dissolved in AIT even in the absence of an organic solvent to givea uniform antimicrobial solution. The antimicrobial composition has goodstability and provides easily an oil-in-water preparation or awater-in-oil preparation that can be uniformly dispersed in water. Theantimicrobial composition of the invention is therefore easy to handle,and is popular, for example, for a food freshness-keeping agent.

1. An antimicrobial composition comprising allyl isothiocyanate and abeta acids-containing hop extract as the active ingredients, wherein theblend ratio of allyl isothiocyanate to the beta acids-containing hopextract is between 5:1 and 1:1 by weight, and the hop extract containsat least 50% by weight of beta acids, which further contains surfactantand water, and is in the form of an oil-in-water preparation.
 2. Theantimicrobial composition as claimed in claim 1, wherein said hopextract is obtained through extraction with liquid or critical-statecarbon dioxide.
 3. A food freshness-keeping agent that comprises theantimicrobial composition of claim
 1. 4. A method of keeping thefreshness of food, which comprises adding the antimicrobial compositionof claim 1 to food.
 5. The antimicrobial composition as claimed in claim1, wherein water is in the amount of 1 to 100 parts by weight relativeto 1 part by weight of the composition and the surfactant having an HLBvalue from 8 to 16 is in the amount of 0.01 to 1 part by weight relativeto 1 part by weight of the composition.
 6. The antimicrobial compositionas claimed in claim 1, wherein said surfactant is selected from thegroup consisting of glycerin fatty acid esters, sucrose fatty acidesters, sorbitan fatty acid esters, propylene glycol fatty acid estersand mixtures thereof.